arm64: dts: qcom: msm8916-samsung-a2015: Rename touchscreen analog regulator

reg_vdd_tsp: regulator-vdd-tsp is actually used as an analog regulator for
touchscreen on all of a2015 and e2015 devices.
Rename it into reg_vdd_tsp_a: regulator-vdd-tsp-a to reduce confusion.

Signed-off-by: Lin, Meng-Bo <linmengbo0689@protonmail.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220724095438.14252-1-linmengbo0689@protonmail.com